KM - what time is he napping most days? We had an issue with EW at same age as your DS. At the time, my DS started waking around 5.30am, he was napping 11/11.30am for up to 2hrs & bed 6.30ish (earlier if nap was shorter). We were constantly doing early naps & EBT to try & prevent him getting OT from his EW & I eventually learned this was actually fuelling it. What we did was very slowly, push DS's nap later, by 15mins per week. I let him sleep 2hrs max & did BT 5hrs later. So:
Week: 1 Nap: 11.15-1.15 BT: 6.15
Week: 2 Nap: 11.30-1.30 BT: 6.30
Week: 3 Nap: 11.45-1.45 BT: 6.45
Week: 4 Nap: 12.00-2.00 BT: 7.00
In the first couple of weeks there were some days when he still woke early & he had a 7hr A before his nap, and he short napped, but we stuck with it & eventually his bodyclock 'clicked'. It was tough, & maybe not the preferred route for everyone (since it does push them to the brink of exhaustion), but it really did work. We found we had to get him to a 12.30pm nap for 2hrs & a 7/7.30pm BT in order to see a radical improvement in his EW.
HTH.x